Untitled Flashcard Set

Thales

Proposed that the basic substance of everything is water.

Apeiron

The concept proposed by Anaximander meaning boundless or infinite.

Anaximenes

Believed air was the basic substance of everything, transforming through compression and expansion.

Heraclitus

Philosopher who believed fire was the fundamental substance and that everything is constantly changing.

Xenophanes

Introduced the idea that the basic substances were earth and water, questioning traditional nature explanations.

Aristotle's Four Elements

Matter consists of earth, water, air, and fire, associated with qualities of hot, cold, wet, and dry.

Atomos

A term by Democritus and Leucippus meaning 'indivisible' to describe tiny particles of matter.

John Dalton

Developed the first modern scientific atomic theory based on experimental evidence in the early 1800s.

Dalton's Solid Sphere Model

Depicted an atom as a small, solid, indivisible sphere, without electrons, protons, or neutrons.

Postulate 1

All matter is composed of extremely small particles called atoms.

Postulate 2

Atoms of the same element are identical in their properties and mass; different elements have different properties.

Postulate 3

Atoms cannot be created, destroyed, or divided during a chemical reaction.

Postulate 4

Atoms combine in simple whole-number ratios to form compounds.

Postulate 5

Atoms are rearranged during chemical reactions.

Amended Postulate

Atoms can be divided into smaller particles: protons, neutrons, and electrons.

Isotopes

Atoms of the same element that can have different masses due to varying numbers of neutrons.

Dalton's Theory Consistency

Matter is made of atoms; elements consist of atoms; atoms combine to form compounds; chemical reactions involve rearrangement of atoms.